Suppose $f:(-\pi / 2, \pi / 2) \rightarrow \mathbb{R}$ is a continuous function such that $f(x)=\frac{\sqrt{9-x}-\sqrt{9+x}}{\sin x \cos x}$ for all $x \neq 0$. Then the value of $f(0)$ is

• A

  $-\frac{1}{9}$
• B

  $-\frac{1}{6}$
• Correct answer
  C

  $-\frac{1}{3}$
• D

  0

Hence, the correct answer is option: 'C'.